Editing Wader (section)

=== Natural selection ===
Another factor that leads to the development of dimorphisms in species is [[natural selection]].  Natural selection focuses on traits and the environment's response to the traits in question; if the said trait increases the overall fitness of the individual possessing it, then it will be 'selected' and eventually become a permanent part of the population's gene pool. For example, depending on the food available in a shorebird specie's respective [[Ecological niche|niche]], bigger bill sizes may be favored in all individuals.<ref name=":0" /> This would essentially lead to monomorphism within the species but is subject to change once sexual selection acts on the trait. Sexual selection could give rise to males with relatively larger bills than females if males used their bills to compete with other males. If larger bill size assisted the male in gathering resources, it would also make him more attractive to female mates.<ref name=":1" />